[Veedrac]

There clearly is a change in structure somewhere, even if the precise location is arguable, since extremely small brains are fixed in structure (every connection is deterministic) and seem to implement completely fixed programs.

I imagine the transition will be fairly fluid, with ants running a mix of sophisticated hardwired programs and more simple learned associations (and even humans having a degree of fixed-function behaviours), but that's not to say a distinction can't be made.